1. Field of the Invention
The present invention relates to a portable display device, and more particularly to a portable display device having a reduced thickness.
2. Description of the Related Art
Recently, various flat plate displays capable of reducing weight and volume that are disadvantages of Cathode Ray Tubes (CRTs) have been developed. Flat panel displays include Liquid Crystal Displays (LCDs), Field Emission Displays (FEDs), Plasma Display Panels (PDPs), and organic light emitting displays.
Because LCDs have advantages including small-size, light-weight and low-power requirements, they have come into the spotlight as a substitute for CRTs. Recently, LCDs have been mounted in portable devices, such as portable phones, Personal Digital Assistants (PDAs), monitors, and TVs.
FIG. 1 is an exploded perspective view of a conventional portable display device. FIG. 2 is a cross-sectional view of the portable display device of FIG. 1 taken along line A-A′. FIG. 1 and FIG. 2 show a dual type display device, which includes a liquid crystal display panel and an organic light emitting display panel.
With reference to FIG. 1 and FIG.2, the conventional portable display device 100 includes an organic light emitting display panel 110, a first printed circuit board 120, a second printed circuit board 130, a Liquid Crystal Display (LCD) panel 148, and a bottom chassis 140 for receiving a backlight assembly. A flexible printed circuit board 114 is located on one side of the organic light emitting display panel 110. An integrated circuit 116 is mounted on the flexible printed circuit board 114 and provides a drive signal to the organic light emitting display panel 110. The flexible printed circuit board 114 is mounted in such as way that a part thereof is bent.
A plurality of Organic Light Emitting Diodes (OLEDs) (not shown) are arranged in the organic light emitting display panel 110 in the form of a matrix. The OLEDs generate light of a predetermined luminance corresponding to a drive signal supplied thereto. In order to supply the drive signal, the flexible printed circuit board 114 is positioned on one side of the organic light emitting display panel 110, and the integrated circuit 116 is mounted on an upper portion of the flexible printed circuit board 114. One side of the flexible printed circuit board 114 is positioned on a lower side portion of the organic light emitting display panel 110 to be connected to the organic light emitting display panel 110. A pad portion (not shown) of the flexible printed circuit board 114 is connected to a first pad portion 122 of the first printed circuit board 120 by soldering. The flexible printed circuit board 114 has a laminate structure of at least two materials having different thicknesses. A lower layer of the flexible printed circuit board 114 is generally thicker than an upper layer thereof. Accordingly, upon soldering the flexible printed circuit board 114 and the first printed circuit board 120, a bad soldering joint can occur due to stepped portions according to directions of materials. In order to prevent an occurrence of the bad soldering joint, the upper layer having a small thickness should be jointed to the first printed circuit board 120. To do this, conventionally, after a part of the flexible printed circuit board 114 is bent and a pad portion of the flexible printed circuit board 114 contacts the first pad portion 122, soldering is performed. When the pad portion of the flexible printed circuit board 114 is joined to the first pad portion 122, control signals generated by the first printed circuit board 120 are transferred to an integrated circuit 116, which is mounted on the flexible printed circuit board 114. Then, the integrated circuit 116 generates and provides drive signals corresponding to the control signals to the organic light emitting display panel 110, with the result that the organic light emitting display panel 110 displays a predetermined image. A metal plate 112 is attached to a lower portion of the organic light emitting display panel 110, and protects the organic light emitting display panel 110 from the infiltration of moisture.
The first printed circuit board 120 receives a drive signal from a drive circuit (not shown) of a portable phone. To do this, the first printed circuit board 120 includes a portable phone connector 125. The portable phone connector 125 mates with another connector attached to a drive circuit of a portable phone, and receives a drive signal from the drive circuit of a portable phone. The first printed circuit board 120, having received the drive signal, generates various control signals corresponding to the drive signal. At least a part of the metal plate 112 is inserted into an opening portion, which is formed in a predetermined portion of the first printed circuit board 120.
The second printed circuit board 130 is connected to the first printed circuit board 120 through a second pad portion 132. Furthermore, the second printed circuit board 130 is connected to an integrated circuit and an OLED board (not shown) of the LCD panel 148, having layers 148a and 148b, through a flexible printed circuit board (not shown). The second printed circuit board 130 connected to the integrated circuit and the OLED board drives the integrated circuit and the OLED board according to the control signals from the first printed circuit board 120.
The bottom chassis 140 engages with a molded frame 141 included in a backlight assembly, and receives the LCD panel 148 and the backlight assembly. The LCD panel 148 displays a predetermined image corresponding to a drive signal supplied thereto. The backlight assembly supplies predetermined light to the LCD panel 148 so that the liquid crystal display panel can display an image. In order to do this, the backlight assembly includes a Light Emitting Diode (LED) board (not shown), a reflective plate 142, a light guide plate 144, and optical sheets 146. Light sources, such as Light Emitting Diodes (LEDs) are mounted on the LED board.
In the aforementioned conventional portable display device 100, it is necessary to reduce a total thickness of the display device in order to be easily carried. A protrusion of the OLED panel 110 is one factor that increases the thickness of the portable display device 100. The flexible printed circuit board 114 in which an integrated circuit 116 is mounted is bent and mounted. Accordingly, the integrated circuit 116 can protrude. This can be a factor to increase the thickness of the portable display device 100. So as to minimize protrusions of the OLED panel 110 and the integrated circuit 116, a way of reducing a thickness of the portable display device 100 is needed.